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Article

Age-Based Demography of Two Parrotfish and a Goatfish from Saipan, Northern Mariana Islands

by
Cassandra Pardee
1,*,
John Wiley
1 and
Brett M. Taylor
2
1
Poseidon Fisheries Research, Kalaheo, HI 96741, USA
2
Sea Grant and Marine Laboratory, University of Guam, Mangilao, GU 96923, USA
*
Author to whom correspondence should be addressed.
Fishes 2025, 10(7), 303; https://doi.org/10.3390/fishes10070303
Submission received: 29 April 2025 / Revised: 30 May 2025 / Accepted: 17 June 2025 / Published: 24 June 2025
(This article belongs to the Section Biology and Ecology)
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Abstract

The age-based life history of two commercially important parrotfishes (Labridae: tribe Scarinae) and one goatfish (Mullidae) were characterized based on the commercial nearshore fishery in Saipan, Commonwealth of the Northern Mariana Islands. Age, growth, reproduction, and mortality were derived from fishery-dependent samples using sagittal otoliths and gonads for the stareye parrotfish Calotomus carolinus, pacific bullethead parrotfish Chlorurus spilurus, and yellowfin goatfish Mulloidichthys vanicolensis. All three species had short lifespans of 10 years or less, with a maximum age of 4 years for C. carolinus, 10 years for C. spilurus, and 7 years for M. vanicolensis. All three species had a fast initial growth to terminal body sizes, early maturation, and spawned throughout the year. The age-based demographic information presented here can be used to inform future stock assessments, fisheries management, and population models.
Keywords:
life history; otolith; Northern Mariana Islands; parrotfish; goatfish
Key Contribution: This study provides the first age-based demographic profiles for Calotomus carolinus, Chlorurus spilurus, and Mulloidichthys vanicolensis from Saipan, offering essential life-history parameters that are directly applicable to stock assessments and fisheries management in the Northern Mariana Islands.

1. Introduction

Coastal fisheries are an integral component of food security and perpetuate cultural practices of island communities throughout the Indo-Pacific. These fisheries are comprised of numerous coral reef-associated species that represent a wide range of trophic levels, ecosystem roles, and life-history traits. Basic biological information for targeted species represents the cornerstone for inferring vulnerability to overexploitation and for developing sustainable management strategies [1,2,3]. Unfortunately, tropical fisheries of the Indo-Pacific are data-limited with relatively little information known about the growth and maturation of commonly targeted coral reef species [4,5,6]. Further, life-history characteristics can vary across spatial scales, thus, commonly studied species may still require region-specific empirical estimates of trait values for accurate assessments.
Within the Commonwealth of the Northern Mariana Islands (CNMI), parrotfishes (family: Labridae; tribe: Scarine) and goatfishes (family: Mullidae) represent two of the top three targeted fish families along with surgeonfishes (family: Acanthuridae) [7]. Both parrotfish and goatfish families consist of multiple species with variable lifespans, growth rates, and maturity schedules [8,9,10,11,12]. Both parrotfishes and goatfishes represent diverse families and are found worldwide in both tropical and subtropical waters [13,14] Parrotfishes target benthic and endolithic algal and microbial resources with the capacity to modify the benthos through their feeding strategy [13,15,16]. Parrotfishes are protogynous hermaphrodites and exhibit a wide range of sizes (11 cm to over 100 cm) and ages (3 years to over 30 years) [9,17,18,19,20]. Goatfishes inhabit shallow sandy-bottom habitats and use their barbels to search for prey in the sediment [21,22]. Goatfishes are gonochoristic with a narrower size range (20 cm to 60 cm) and short lifespans (less than 10 years) [8,11,12,22].
In this study, two parrotfishes (stareye parrotfish Calotomus carolinus and Pacific bullethead parrotfish Chlorurus spilurus) and one goatfish (yellowfin goatfish Mulloidichthys vanicolensis) were selected for life-history analysis based on discussions with CNMI fishery managers to aid in the development of their fishery management strategy. These three species are among the top 30 species landed from the commercial nighttime free-diving spear fishery [7]. Examining the complete bio-sampling database from January 2010 through August 2020, Chlorurus spilurus ranked 12th in abundance in the commercial market, while Mulloidichthys vanicolensis ranked 13th, and Calotomus carolinus ranked 28th. This database includes 3086 commercial catches comprising 233,287 individual fish measurements and 205 different species [23].
All three selected species are commonly targeted throughout the Indo-Pacific region and have age-based life-history information documented from other areas [8,9,10,12,24]. Each species is reported to be short-lived (≤11 years) with a high growth coefficient, and reaches reproductive maturity within two years [9,10,12]. Even in Hawaii, where colder winter ocean temperatures generally elicit longer lifespans in ectotherms, these species are short-lived; C. carolinus, C. spilurus, and M. vanicolensis reach maximum ages of 4, 11, and 5 years, respectively [8,10]. In Okinawa Island, Japan, M. vanicolensis reach a maximum age of 7 years [12]. In lower latitude regions of Guam, C. carolinus and C. spilurus have maximum ages of 3 and 9 years, respectively [9]. While there is no age and growth information for M. vanicolensis from lower latitudes, a similar goatfish species Mulloidichthys flavolineatus has a maximum age of 5 years for Saipan based on the same bio-sampling data used for this study [11].
This study aims to determine age-based life-history information from fishery-dependent samples of two parrotfish and one goatfish species which are targeted within the nighttime free-diving spear fishery of Saipan. The primary objectives are to estimate growth parameters, lifespan, and mortality using age information derived from otoliths; and determine maturity, size at sex-change, and spawning patterns. The Saipan specific life-history information from this study will help facilitate future management of these commercially and culturally important species.

2. Materials and Methods

2.1. Study Site and Sampling

Samples of C. carolinus, C. spilurus, and M. vanicolensis were collected from commercial catches landed in Saipan, Northern Marianas (Figure 1; 15°14′ N, 145°43′ E) as part of the NOAA-funded CNMI bio-sampling program, which collects species-specific commercial fisheries data in the Central and Western Pacific US jurisdictions [23]. The Saipan bio-sampling program was established to collect reef fish life history data from commercial free-diving spear fishers whose catches were landed on Saipan and sold at local markets. Data collection commenced in 2010 and stopped in 2017. This study used a subset from December 2014 through April 2017, of the larger bio-sampling database.
Survey methods and sampling protocols are detailed in Sundberg et al. 2015 and Trianni et al. 2018 [7,25]. Fish specimens were purchased directly from commercial nighttime free-diving spear fishers and local vendors. Vendors were sampled two to three times a week (2 weekdays, 1 weekend day) during the early morning hours (0330–0630) [7]. Samplers processed catches directly after vendor purchase to ensure that sampled catches were unique and complete [7]. For each specimen, capture date, fork length (FL) to the nearest 0.1 cm, and total body weight in grams were recorded. Sex was macroscopically identified as either male, female, or unknown based on exterior coloration for the parrotfish coupled with visual gonad inspection. Gonads were weighed to the nearest 0.001 g, and sections of gonadal tissue were excised and stored in individual labeled histology cassettes and stored in a 10% buffered formalin solution. Paired sagittal otoliths were collected from the skull cavity and cleaned with water and stored dried.

2.2. Reproduction

Subsamples of C. carolinus, C. spilurus and M. vanicolensis were selected for histological processing and staging. Fixed gonad samples were processed at the University of Hawaii John Burns Medical School; embedded in paraffin wax, sliced into thin transverse sections, and stained with hematoxylin and eosin [26]. Specimens were classified as male, female, or transitional using a compound microscope with transmitted light. Females were further classified based on the developmental stage using the modified terminology of Brown-Peterson et al. 2011 [27]: immature, developing, spawning-capable, actively spawning, regressing, or regenerating, where the onset of vitellogenesis was used as the criteria for maturity (Figure 2). Transitional individuals were identified by having atretic oocytes within the proliferating testicular tissues, but did not have peripheral sperm sinuses containing spermatozoa [28].
Length at 50% maturity (L50) was estimated by fitting a binomial logistic curve to the proportion of mature individuals per length class using 2 cm bins. The logistic curve was defined by P L = 1 + e − l n 19 L − L 50 L 95 − L 50 − 1 , where PL represents the estimated proportion of mature females at length (L), and L50 and L95 represent the FL when 50% and 95% of the population is mature, respectively. Corresponding 95% confidence intervals (CI) for each parameter were derived using bootstrap resampling (1000 iterations). The same process was used to estimate age at 50% maturity (A50), and length at sex change for both parrotfish species (LΔ50), with lengths indicated by LΔ50 and LΔ95.
Spawning season was assessed by plotting the gonadosomatic index ( G S I = G o n a d   w e i g h t g B o d y   w e i g h t   g × 100 ) of mature females across the calendar year. GSI data were pooled by calendar month because interannual sample numbers were too small to detect reproductive patterns. GSI values were also assessed against lunar day for all mature females combined to examine patterns across a single lunar cycle.

2.3. Age, Growth, and Mortality

Random subsamples of C. carolinus, C. spilurus, and M. vanicolensis were selected for age and growth analysis. A single sagittal otolith from each specimen was weighed to the nearest 0.1 mg and attached to a glass microscope slide using Crystalbond 509® (Aremco Products, Valley Cottage, NY, USA), a thermoplastic glue. The otolith was prepared using methods described in Taylor et al. 2017 [6]. The otolith was attached to the slide edge and the core was positioned just inside the edge. The otolith was ground to the core using a 600 grit diamond lap on a grinding wheel with continuous water flow. The otolith was then removed and reattached to the slide on the flat surface and ground a second time to produce a thin (≤220 µm) transverse section encompassing the core material. Finally, the otolith was covered with a thin layer of Crystalbond 509® to improve clarity.
Sagittal otoliths for all species consistently displayed alternating translucent and opaque bands representing annual growth (annuli) that reflect those of validated samples from other localities (Figure 3) [9,10,29]. Blind reads of opaque growth zones were counted independently along the face of the otolith section using transmitted light on a stereo microscope. Counts were performed two to three different times by the same reader for each specimen. The final age was determined when at least two counts agreed. Juvenile samples of M. vanicolensis less than 16 cm were prepared in the same fashion as above and then further polished using a progression of lapping film (9.0, 3.0, and 1.0 μm grit) to expose daily growth increments. Age in daily growth increments was estimated as the mean of three independent and nonconsecutive age-readings.
The relationship between otolith weight and age was measured using a linear regression to determine if otolith weight was a reliable indicator of age. Sex-specific and combined growth parameters were estimated from length-at-age data using the von Bertalanffy growth function (VBGF) represented by L t = L ∞ 1 − e − K t − t 0 , where Lt is the mean FL (cm) at age t (years), L ∞ is the mean asymptotic FL (cm), K is the growth coefficient towards L ∞ , and t0 is the theoretical age at which the FL is equal to zero. Because specimens were collected through the commercial fishery, there were no recently settled samples in the data set. Therefore, the y-intercept of the fitted VBGF growth curve was constrained to 1.5 cm for both C. carolinus and C. spilurus and 3 cm for M. vanicolensis based on size at settlement [30,31].
Total mortality (Z) was estimated with age frequency distributions using a linear catch curve with knife-edge selectivity. Mortality was defined as the absolute value of the slope of the line fitted to the natural logarithm of the observed frequency of harvested individuals at age t for the corresponding age classes above full recruitment (trec), the age at which fish are fully recruited into the fishery [32]. Full recruitment was set at the peak age frequency instead of one plus peak age because both species were deemed too young to conservatively discard age classes.
Fishing mortality (F) was calculated as total mortality (Z) minus natural mortality (M). An estimate of natural mortality was calculated using Hoenig 1983 equation M = e 1.46 − 1.01 ∗ l n t m a x [33]. Natural mortality was assumed to be constant across age classes.

3. Results

A total of 427 C. carolinus, 723 C. spilurus, and 985 M. vanicolensis commercial specimens were measured, weighed, and gonads excised for life-history investigations. Length-frequency distributions from the commercial harvest are displayed in Figure 4. All three species showed sex-specific distributions. For M. vanicolensis the modal size of the females was greater than that of the males, while for both C. carolinus and C. spilurus the modal sizes of males were greater than females.

3.1. Reproduction

We confirmed sexual identity and characterized female maturation profiles using histological sections of gonads from 367 C. carolinus (150 females), 454 C. spilurus (218 females) and 380 M. vanicolensis (217 females). We estimated length at maturation (L50) for M. vanicolensis as 18.9 cm FL (95% CI: 18.6–19.2) and the age at maturity (A50) as 1.9 years (1.6–2.1 years) (Table 1; Figure 5c). For both parrotfish species, fishery selectivity largely targeted individuals above the length and age ranges over which female maturation occurred. Hence, the fisheries-dependent sampling program resulted in near-complete overlap of immature and mature individuals in the smallest sampled size classes for C. spilurus, and to a lesser extent in C. carolinus (Figure 5a,b). As a result, we empirically estimated the length at maturation (L50) for C. carolinus as 18.6 cm FL (17.9–19.1) (Table 1). The length-based maturation profile of C. spilurus failed to converge in the logistic model, as did the age at maturity (A50) profile for both species (Table 1).
For both parrotfish species, we found six specimens that contained characteristics of ongoing female-to-male sex change, notably atretic vitellogenic oocytes in the presence of proliferating male material, indicating post-maturational sex change. All C. carolinus males contained evidence of post-maturational sex change, suggesting a single (monandric) protogynous pathway. Initial phase primary males as well as terminal males with no evidence of gonadal change (i.e., no ovarian lumen from histology) were both observed for C. spilurus, suggesting a diandric pathway (Figure 6). Individuals that were actively transitioning were observed from 20.7 to 28.0 cm FL in C. carolinus and from 19.3 to 23.9 cm in C. spilurus (Figure 3). The length at median sex change (LΔ50) was estimated as 24.2 cm and 21.0 for C. carolinus and C. spilurus, respectively (Figure 7; Table 1).
Spawning-capable and actively spawning females were observed for all three species across all months, with no species showing strong patterns of gonadosomatic index (GSI) change across time (Figure 8a,c,e). Calotomus carolinus female GSI peaks during February-March based on the multiyear aggregated data (Figure 8a), although this pattern was not consistent across years. Mulloidichthys vanicolensis female GSI had the lowest values in July and August (Figure 8e), although these months contained some of the lowest sample sizes.
The lunar patterns of potential spawning activity were equally unclear for C. carolinus and C. spilurus, with very little variability across the lunar phases (Figure 8b,d). Female M. vanicolensis GSI showed variability across the lunar phases with GSI peaking after the full and new moon (Figure 8f).

3.2. Age Determination, Growth, and Mortality

Ages were estimated from sagittal otoliths from a total of 303 specimens for C. carolinus, 453 specimens for C. spilurus, and 400 specimens for M. vanicolensis (Table 1). All species deposited clearly defined annuli that were highly characteristic of otolith patterns previously identified and validated for these species (Figure 3; [9,10,29]). Otolith weight (g) was a linear predictor of age for all three species (Figure 9).
All three species had short lifespans of 10 years or less (Table 1). Calotomus carolinus had the smallest maximum observed age of 4 (both sexes), M. vanicolensis had a maximum observed age of 7 years, and C. spilurus was the oldest-lived species of 10 years (9 for females). For both parrotfish species, males grew to a larger asymptotic length than females, although this difference was more pronounced in C. carolinus (Figure 10a,b). In M. vanicolensis, females reached a larger asymptotic length than males (Figure 10c).
Overall VBGF parameter values L∞ and K for the combined sexes were as follows: C. carolinus, L∞ = 26.4 cm, K = 1.94 yr−1; C. spilurus, L∞ = 21.8 cm, K = 0.88 yr−1, and M. vanicolensis L∞ = 21.4 cm, K = 1.27 yr−1. Sex-specific VBGF values and associated confidence limits are presented in Table 1.
Based on the catch at age frequency, all three species fully entered the fishery between 1 to 3 years of age (Figure 11). Total mortality estimates derived from age-based catch curves were 1.301 (1.205–1.397) for C. carolinus, 0.607 (0.557–0.657) for C. spilurus, and 0.686 yr−1 (0.488–0.872) for M. vanicolensis based on data pooled across years (Figure 11; Table 1). Natural mortality (M) was estimated at 1.06 yr−1 for C. carolinus; 0.42 yr−1 for C. spilurus; and 0.60 yr−1 for M. vanicolensis, with the assumption that the maximum ages were adequately characterized within the sample size of the present study. The rate of fishing mortality (F = Z − M) was 0.24 yr−1, 0.19 yr−1, and 0.09 yr−1 for C. carolinus, C. spilurus, and M. vanicolensis, respectively.

4. Discussion

The life-history parameters derived for these three species from the Saipan market were comparable to those previously determined from other regions. Calotomus carolinus, C. spilurus, and M. vanicolensis all had maximum observed ages within one to two years of those from Okinawa, Hawaii, Australia and Guam, suggesting low-to-moderate variability in lifespan across the western Pacific basin [8,9,10,12,20]. The biggest difference in maximum age was between M. vanicolensis from Hawaii (5 years) and this study (7 years); however, the maximum age may be underrepresented for Hawaii since the study had a small sample size of 50 specimens [8]. Mean asymptotic length (L∞) was the same for C. carolinus and C. spilurus between CNMI and Guam [9]. Chlorurus spilurus also had a similar L∞ to specimens from the Great Barrier Reef in Australia [20]. The von Bertalanffy growth coefficient (K) was similar for C. spilurus between Guam and Saipan; however, for C. carolinus, K was more than twice as large in Saipan fish as that determined for Guam (1.94 yr−1 vs. 0.91 yr−1). One possible explanation for the spatial difference in K values (even with a similar max age and L∞) is that the sampling for Saipan was fishery-dependent and lacked smaller size classes to define the rising arm of the growth curve. Future efforts to include these smaller fish in the Saipan analysis would likely decrease the K value closer to what was shown for Guam. Mulloidichthys vanicolensis had similar VBGF parameters to those identified for Hawaii, with Hawaii having a slightly larger maximum size (22.7 cm vs. 21.4 cm) [8].
Size at maturity in Saipan also aligned with size at maturity from other regions. Chlorurus spilurus and M. vanicolensis size at maturity from this study were within the confidence intervals of the sizes at maturity for Guam and Okinawa, respectively [9,12]. We were unable to calculate size at maturity for C. spilurus due to the fishery-dependent sampling structure, restricting the acquisition of smaller-sized immature fish. The smallest females sampled for this study were spawning-capable (16.2 cm) and immature (16.3 cm), supporting an L50 that is likely closer to the smaller size at maturity observed for C. spilurus in Guam of 14.4 cm [9]. Future efforts to supplement the dataset with smaller individuals (<16 cm) are needed to determine the size of maturity for C. spilurus.
Guam and Saipan are part of the southern Mariana Archipelago with similar sea surface temperatures and 214 km separating the two islands. Variations in lifespan between populations are strongly linked to sea-surface temperature [34]. Similar to the species in this study, Naso unicornis showed very little difference in life-history traits between Guam and Saipan [35]. Additionally, several studies have shown high genetic connectivity of coral reef fish between Guam and Saipan, with one study finding a N. unicornis sibling pair between the two islands [36,37]. Biophysical models based on the southern Mariana Islands North Equatorial Current regime also predicted high levels of connectivity across the Mariana Archipelago [38].
Most interestingly, M. vanicolensis life-history characteristics closely matched those from higher latitude regions of Hawaii and Japan. Lower latitudes and higher temperatures usually lead to faster growth and shorter lifespans in ectotherms due to an increase in metabolic processes across thermal gradients [35,39,40]. However, M. vanicolensis had the same maximum age in Saipan as in Okinawa.
Species’ vulnerability to fishing is based on their productivity (life-history traits) and susceptibility (ease of capture) [41,42]. Parrotfish may be highly susceptible to fishing pressure because they have a shallow depth distribution, are very conspicuous, and are easily targeted at night, a fishing strategy that constitutes a majority of the spearfishing pressure in CNMI [43]. Similarly, goatfish may also have a high susceptibility to fishing due to their shallow distribution, schooling nature, and ease of capture. In the Saipan spear fishery, both C. carolinus and M. vanicolensis are primarily landed from shore-based fishing trips within the protected Saipan Lagoon, a relatively heavily fished area, allowing for easy access and protection from weather year-round [7].
Yet even with high susceptibility, a population may have a greater resiliency to high fishing pressure because of high productivity coupled with rapid turnover times. All three species have rapid and productive life-history strategies: fast growth, early maturation, year-round spawning, and a short life span which may allow for more resilient populations. In addition, SCUBA spearfishing is illegal in CNMI, with a primary fishing depth within 15 m allowing for a potential depth refuge for commonly targeted species. Biomass, abundance, fish size, and species richness of commonly targeted reef species increased in depths up to 60 m around CNMI [44,45].
This preliminary study found all three species had a low fishing mortality rate relative to the estimated rate of natural mortality. However, the natural mortality rate assumed that the maximum ages were adequately captured within the sample size of the present study. The observed maximum age for species with shorter lifespans is more likely to come from a cohort represented by a large recruitment event and can be affected by the sampling approach [46]. This data should be used in more comprehensive stock assessments that not only address potential biases in mortality estimations but also consider other critical aspects of the fishery. Further research is necessary to provide a more definitive understanding of the impacts of fishing on these populations and to inform management strategies more reliably.
The species examined in this study—Calotomus carolinus, Chlorurus spilurus, and Mulloidichthys vanicolensis—are all small-bodied, fast-growing fishes with short lifespans and early maturity, characteristics that confer high turnover and resilience to fishing pressure. Importantly, the fisheries-dependent data reveal that the majority of harvested individuals are already mature, indicating that traditional size-based management approaches (e.g., minimum size limits) would have limited conservation value for these taxa. Instead, sustainable fishery management for these species should prioritize controlling fishing effort, such as gear restrictions, effort caps, or spatial/temporal closures. The life-history parameters generated here—including age at maturity, growth coefficients, and mortality estimates—can be directly integrated into length-based or age-structured stock assessment models, including data-limited methods such as Length-Based Spawning Potential Ratio (LB-SPR) or catch-only models. These parameters can also serve to improve ecosystem-based management approaches by refining ecological models that simulate population dynamics under various fishing and climate scenarios. As such, the trait values and demographic benchmarks presented offer essential tools for species-specific, context-relevant management planning in the CNMI and similar reef fisheries.

5. Conclusions

Parrotfish and goatfish are highly targeted families within the Saipan nearshore coral reef fishery by commercial night-time free-diving spear fishers. All three species in this study exhibit highly productive life-history traits, potentially rendering them less vulnerable to high fishing pressure. Our results offer location-specific life history information that will aid fishery scientists and managers in future stock assessments and fishery management within the region.

Author Contributions

Idea: C.P., B.M.T. and J.W.; data analysis: C.P. and B.M.T.; figure formatting: B.M.T.; manuscript preparation: C.P. and B.M.T.; funding acquisition: C.P. and J.W. All authors have read and agreed to the published version of the manuscript.

Funding

Funding for this study was provided by the Western Pacific Regional Fishery Management Council through a NOAA Coral Reef Conservation Program Cooperative Agreement (NA22NMF4410183), and in part by a Saltonstall-Kennedy Grant Program grant (NA17NMF4270226) awarded to Micronesian Environmental Services and was supported by the National Marine Fisheries Service Bio-sampling initiative. This project was also supported by the Histopathology Core at the John Burns Medical School University of Hawaii, grant number U54MD007601 from the National Institute on Minority Health and Health Disparities, National Institutes of Health.

Institutional Review Board Statement

All fish specimens used in this study were either purchased from local vendors or donated. No live animals were handled, and no animal experiments were conducted as part of this research. Therefore, ethical approval was not required for this study.

Data Availability Statement

Data can be requested from the NOAA Pacific Island Fisheries Science Center Life History Division. All samples and data used in this publication are from Pacific Island Fisheries Science Center 2024: CNMI Commercial Fisheries Bio-Sampling (CFBS). https://www.fisheries.noaa.gov/inport/item/5633 (accessed on 6 February 2024).

Acknowledgments

We thank the CNMI Bio-sampling team, Micronesian Environmental Services, (Mike Trianni, Mike Tenorio, Trey Dunn, Ray Roberto, John Castro, Tony Flores, Patrick Ito, George Salas, Anthony Manibusan, Jake Flores, Miguel Naputi, Lucio Kalen, Jan Reyes, Shirley Ann Deleon Guerrero, Max Garcia, Jay Camacho, and John Gourley) for their efforts in collecting fishery samples. A special thanks to those fishers and roadside vendors who worked with the Bio-sampling team in allowing access to their catch and markets (Roadside Fish Market, DJ Fish Mart, Asin’s Fish Mart, JOH Fish Market, Marianas Fishing, Oram Corporation, Serebu’s, WJC Fish Mart) and without whose support this project would not have been possible. Thanks to Josh DeMello from Western Pacific Regional Fishery Management Council, and T. Todd Jones and Eva Schemmel from the Pacific Island Fisheries Science Center for facilitating data use and input in this manuscript.

Conflicts of Interest

The authors declare that they have no conflicts of interest in relation to this study or its publication.

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Figure 1. Map of the Commonwealth of the Northern Mariana Islands and Guam.
Figure 1. Map of the Commonwealth of the Northern Mariana Islands and Guam.
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Figure 2. Histological staging for Chlorurus spilurus classified as: (a) immature (PG = primary growth oocytes, OG = oogonia); (b) developing (CA = cortical alveoli, VTI and VTII = vitellogenic state 1 and 2 oocytes); (c) spawning-capable (VTIII = vitellogenic stage 3 oocytes); (d) actively spawning (H = hydrated oocytes); (e) regressing (A = atresia); (f) regenerating; (g) transitioning gonads (SC = spermatocytes, SG = spermatogonia); (h) male testes (SZ = spermatozoa). Note: scale bar = 1 mm for (a–f); 0.5 mm for (g); and 0.1 mm for (h).
Figure 2. Histological staging for Chlorurus spilurus classified as: (a) immature (PG = primary growth oocytes, OG = oogonia); (b) developing (CA = cortical alveoli, VTI and VTII = vitellogenic state 1 and 2 oocytes); (c) spawning-capable (VTIII = vitellogenic stage 3 oocytes); (d) actively spawning (H = hydrated oocytes); (e) regressing (A = atresia); (f) regenerating; (g) transitioning gonads (SC = spermatocytes, SG = spermatogonia); (h) male testes (SZ = spermatozoa). Note: scale bar = 1 mm for (a–f); 0.5 mm for (g); and 0.1 mm for (h).
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Figure 3. Photomicrographs of transverse otolith sections for (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis. Annual increments (opaque bands) are denoted by white markers. Black bars represent 1 mm.
Figure 3. Photomicrographs of transverse otolith sections for (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis. Annual increments (opaque bands) are denoted by white markers. Black bars represent 1 mm.
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Figure 4. Sex-specific length-frequency distributions: females (red bars), males (green bars), and transitioning/unknown sex (blue bars) for (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis.
Figure 4. Sex-specific length-frequency distributions: females (red bars), males (green bars), and transitioning/unknown sex (blue bars) for (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis.
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Figure 5. Size at maturity (cm) for (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis where 1 indicates mature and 0 indicates immature. The red dotted line represents the length at 50% maturity.
Figure 5. Size at maturity (cm) for (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis where 1 indicates mature and 0 indicates immature. The red dotted line represents the length at 50% maturity.
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Figure 6. Photomicrograph of (a) 20.3 cm Chlorurus spilurus primary male with no ovarian lumen, and (b) a 24.7 cm Chlorurus spilurus secondary male showing ovarian lumen.
Figure 6. Photomicrograph of (a) 20.3 cm Chlorurus spilurus primary male with no ovarian lumen, and (b) a 24.7 cm Chlorurus spilurus secondary male showing ovarian lumen.
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Figure 7. Size at sexual transition (cm) for (a) Calotomus carolinus, and (b) Chlorurus spilurus, where 1 indicates male and 0 indicates female. The red dotted line represents the length at 50% sexual transition.
Figure 7. Size at sexual transition (cm) for (a) Calotomus carolinus, and (b) Chlorurus spilurus, where 1 indicates male and 0 indicates female. The red dotted line represents the length at 50% sexual transition.
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Figure 8. Female and male gonadosomatic index (GSI) (a,c,e) per month and per lunar day (b,d,f) for Calotomus carolinus (top), Chlorurus spilurus (middle), and (c) Mulloidichthys vanicolensis (bottom). The numbers above the plots indicate sample size per month. Open/white and closed/black circles represent full and new moons, respectively.
Figure 8. Female and male gonadosomatic index (GSI) (a,c,e) per month and per lunar day (b,d,f) for Calotomus carolinus (top), Chlorurus spilurus (middle), and (c) Mulloidichthys vanicolensis (bottom). The numbers above the plots indicate sample size per month. Open/white and closed/black circles represent full and new moons, respectively.
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Figure 9. Sex-specific relationships between sagittal otolith weight (g) and annual age (represented by number of annuli) for (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis.
Figure 9. Sex-specific relationships between sagittal otolith weight (g) and annual age (represented by number of annuli) for (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis.
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Figure 10. Sex-specific and combined von Betalanffy growth curves for: (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis. The solid line represents the combined best fit curve for both sexes for each species. See Table 1 for parameter estimates.
Figure 10. Sex-specific and combined von Betalanffy growth curves for: (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis. The solid line represents the combined best fit curve for both sexes for each species. See Table 1 for parameter estimates.
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Figure 11. Age-based catch curve for (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis. The solid line represents the fitted regression catch curve to calculate Z, and the shaded region defines the 95% confidence envelope.
Figure 11. Age-based catch curve for (a) Calotomus carolinus, (b) Chlorurus spilurus, and (c) Mulloidichthys vanicolensis. The solid line represents the fitted regression catch curve to calculate Z, and the shaded region defines the 95% confidence envelope.
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Table 1. Summary of life-history traits for three commercially harvested species form Saipan, CNMI.
Table 1. Summary of life-history traits for three commercially harvested species form Saipan, CNMI.
Calotomus carolinusChlorurus spilurusMulloidichthys vanicolensis
MalesFemalesCombinedMalesFemalesCombinedMalesFemalesCombined
L∞ (cm)26.9
(26.5–27.3)		24.8
(24.1–25.5)		26.4
(26.0–26.8)		22.2
(21.8–22.6)		21.3
(20.9–21.7)		21.8
(21.6–22.2)		20.3
(19.9–20.8)		22.2
(21.7–22.7)		21.4
(21.1–21.8)
K (year−1)2.46
(2.21–2.84)		1.99 (1.75–2.29)1.94
(1.79–2.12)		0.96
(0.84–1.10)		0.91
(0.83–1.01)		0.65
(0.58–0.73)		1.46
(1.34–1.60)		1.21
(1.11–1.32)		1.27
(1.20–1.36)
n aged173126303195254453158195400
Amax44410910677
L50 (cm)-18.6
(17.9–19.1)		--NA-17.2
(16.9–17.5)		18.9
(18.6–19.2)
L95 (cm) 21.9
(20.7–23.4)		 NA 19.6
(18.8–20.7)		21.4
(20.7–22.3)
LΔ50 (cm)--24.2
(23.8–24.5)		--21.0
(20.6–21.4)		---
Z (year−1)--1.30
(1.21–1.40)		--0.61
(0.56–0.66)		--0.69
(0.49–0.87)
Notes: Associated 95% confidence intervals presented in parentheses where appropriate. L∞ asymptotic length; K growth coefficient; n aged number of specimens used in age analysis; Amax maximum age observed; L50 length at 50% sexual maturity; LΔ50 length at 50% sex change; Z instantaneous total mortality estimate from the catch curve.
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Pardee, C.; Wiley, J.; Taylor, B.M. Age-Based Demography of Two Parrotfish and a Goatfish from Saipan, Northern Mariana Islands. Fishes 2025, 10, 303. https://doi.org/10.3390/fishes10070303

AMA Style

Pardee C, Wiley J, Taylor BM. Age-Based Demography of Two Parrotfish and a Goatfish from Saipan, Northern Mariana Islands. Fishes. 2025; 10(7):303. https://doi.org/10.3390/fishes10070303

Chicago/Turabian Style

Pardee, Cassandra, John Wiley, and Brett M. Taylor. 2025. "Age-Based Demography of Two Parrotfish and a Goatfish from Saipan, Northern Mariana Islands" Fishes 10, no. 7: 303. https://doi.org/10.3390/fishes10070303

APA Style

Pardee, C., Wiley, J., & Taylor, B. M. (2025). Age-Based Demography of Two Parrotfish and a Goatfish from Saipan, Northern Mariana Islands. Fishes, 10(7), 303. https://doi.org/10.3390/fishes10070303

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